Method of constructing continuously reinforced concrete slabs



Nov. 22, 1966 A c WEBER 3,287,475

METHOD OF COI ISTI RUCTING CONTINUOUSLY REINFORCED CONCRETE SLABS Filed May 6, 1963 4 Sheets-Sheet 1 Nov. 22, 1966 A. c. WEBER 3,287,475

METHOD OF CONSTRUCTING CONTINUOUSLY REINFORCED CONCRETE SLABS Filed May a, 1963 4 Sheets$heet 2 Nov. 22, 1966 A. c. WEBER 3,287 4 5 METHOD OF CONSTRUCTING CONTINUOUSLY REINFORCED CONCRETE SLABS Filed May 6, 1963 4 Sheets-Sheet 5 United States Patent Office 3,287,475 Patented Nov. 22. 1966 I Adolph C. Weber, Creve Coeur, Mo., assignor to Laclede Steel Company, St. Louis, Mo., a corporation of Missour! Filed May 6, 1963, Ser. No. 278,167 6 Claims. (Cl. 264-34) This invention relates generally to a method of constructing metal reinforced concrete slabs, or other metal reinforced concrete structures, and particularly to pavements which are reinforced with substantial continuity for great distances.

Heretofore, it has been the practice to provide concrete roadways and other slabs with reinforcement usually in the form of tied or welded mats, or wire mesh; and to provide interruptions in the mats, or wire mesh, at frequent intervals for convenient handling and, so that expansion joints may be established at the given points of interruption. Such expansion joints have been deemed necessary to permit the pavement, or slab, to respond to variations in temperature without creating cracks, or openings through the concrete of a magnitude such as to result ultimately in the disintegration of large segments of the pavement or slab. In concrete roadways constructed in those areas where the temperature may vary from sea-son to season, as much as 75 F., or more, it has been customary to provide such expansion joints at in tervals of about 50 feet.

Such expansion joints add substantially to the cost of constructing the roadway, and many of the types of expansion joints heretofore used require constant attention for maintenance.

It is therefore an object of the present invention to provide a method for construction of a continuously reinfor-ced concrete slab wherein the necessity for expansion joints is virtually eliminated.

The mats, or wire mesh, heretofore used for reinforcing concrete roadways, and other such slabs which are exposed to the weather, has heretofore consisted of mats of wire mesh, such as No. 2/0 and No. 3 smooth wire arranged in right angular relationship and welded together at the crossovers. For structural purposes, under no circumstances, is the gauge of the cross wires, or rods, more than 5 less than the lengthwise rods. The stresses transmitted to the mat from the monolithic body in which it was embedded are sustained, in effect, by the several weldments. Consequently, the reinforcement depended upon the strength of the weldments for its anchorage in the monolithic body, and for its reinforcing effect. This characteristic of the mat fixes the minimum size of the wires.

Generally stated, the invention contemplates the provision of wire mesh when placed in the form of substantially fiat mats whose length is several times their width, and whose longitudinally extending wires, or rods, are deformed so as to provide, throughout their length, alternating radially-thick and radially-thin sections (preferably the radially-thick sections are projections as distinguished from notches), so that such wires, or rods, provide their own anchorage within the monolithic body, and thereby free the connections between the longitudinal wire, or rods, and the cross wires of the stresses and strains to which such connections have heretofore been subjected in use.

In concrete slabs which are exposed to the weather, the magnitude of the expansion and contraction which is to be expected depends upon the dimensional magnitude of the slab; the longer a given dimension, the greater the expected contraction and expansion in that direction; and, consequently, where a slab is longer than it is wide, the

stresses and strains imposed upon the reinforcing members which run in the longer direction are perforce greater than those which run in the shorter dimension.

The wire mesh mats, for use as hereinafter described, preferably have their cross Wires of substantially smaller size than the longitudinal wires, a feature which not only conserves material and reduces cost, but also lessens the weight of a mat of given size, and thereby facilitates its handling and installation. Such cross wires may be smooth, but preferably are likewise deformed throughout their lengths to provide alternating radially-thick and radially-thin sections. In the case of the cross wires, it is also advantageous that the successive radially-thick and radially-thin sections be not oriented in rectilinear alignment, but rather progressively vary in their orientation about the axis of the wire, so as to present a generally spiral appearance. While, for the sake of economy, smooth cross wires are to be recommended for concrete pipe, and where the dimension of the slab, parallel to the direction in which the cross wires are to run, is not of such magnitude as to require much reinforcement (e.g., no more than the strength of the interconnecting weldment will sustain), the use of deformed wire which provides its own anchorage in the monolithic body is to be recommended when the magnitude of the slab is such that reinforcement is required in the direction of the cross wires.

The invention further contemplates a mode of application of the wire mesh mats above described, whereby sub stantially continuous longitudinal reinforcement by wires, which provide their own anchorage, is accomplishable in concrete slabs of practically infinite length and with great facility. Specifically, the invention contemplates the provision of wire mesh mats which, when used, are substantially flat, substantially longer than they are wide (i.e., the longitudinal wires are longer than the cross wires), and of sufficiently light weight as to require no more than two men in the handling and laying thereof. In accordance with one embodiment, a mat, fifty-two inches wide and twenty-five feet and four inches long, weighs in the neighborhood of one hundred and eighty pounds when composed of eleven longitudinal wires having a cross-sectional area in square inches of 0.184, which figure is based upon the weight per linear inch of these wires in pounds divided by 0.2833 (weight of one cubic inch of steel), or a calculated diameter in inches of 0.485 (the corresponding diameter of plain wire having the same weight per linear foot); and, nineteen cross wires having a cross-sectional area in square inches of 0.054, which figure is based upon the weight per linear inch of these wires in pounds divided by 0.2833 (weight of a cubic inch of steel), or a calculated diameter in inches of 0.261 (the corresponding diameter of plain wire having the same weight per linear foot). The longitudinal wires are spaced four and one quarter inches center to center and the cross wires are spaced sixteen inches center to center. The longitudinal wires project eight inches beyond the center of the cross wires at each end of the mat. The cross wires project an inch beyond the center of the longitudinal wire along one edge of the mat and eight and one-half inches beyond the center of the longitudinal wire at the opposite edge of the mat. As previously indicated, such mats are, in accordance with the present invention, laid with their longitudinal (i.e., heavier and stronger) wires running parallel to the length of the slab in which they are to the embedded, and their cross wires running substantially parallel to the width or narrower dimension of the slab. Given a suitable substructure, preferably itself a slab of freshly poured concrete of, say, three and one-half inches depth, such mats are preferably laid commencing at one or both sides and Working toward the middle. The first mat is laid flat upon the substructure; the next mat longitudinally thereof is laid in the same manner with its end overlapping the end of the first laid mat for a few (for example, sixteen) inches, but not necessarily with a cross wire of the second overlapping a cross wire of the first; the next mat inwardly (i.e., toward the center of the slab from the first laid mat) is then laid on the substructure so that its edge, which borders on the first laid mat, overlaps the extremities of the cross wires in the first laid mat for a few (for example, five and one quarter) inches, but with the characteristic, however, that the ends of the first laid mat are at least a mat-width distant longitudinally from the ends of the sidewise neighboring mats. In other words, every joint between mats which overlap each other end-wise is bridged by the sidewise neighboring mat. In order to accomplish such staggering of the endwise joints in adjacent rows of mats, it is desirable to provide offstandard sized mats at the beginning and at the end of a length of monolithic pavement constructed in accordance with the present invention. For example, where the mats are fifty-two inches wide and twenty-five feet and four inches long, and the pavement is to be twenty-four feet wide, six rows of mats are required to complete the width of the pavement; and the beginning, at least three, and preferably five, of the mats will be of lesser length than twenty-five feet. For example, if five off-standard length mats are utilized at the beginning, one may be five feet, four inches, another nine feet, four inches, another thirteen feet, four inches, another seventeen feet, four inches, and another twenty-one feet, four inches, in which event the overlapping joint at the ends of the mats in no one row will be aligned crosswise with such joint in another row, and every such joint will be at least approximately a mat-width distantfrom such alignment. After the off-standard sized mats are utilized at the beginning, the standard sized mats may be used to the exclusion of off-standard sized ones throughout the length of the pavement until the end is reached, whereupon another set of off-standard sized mats will usually be required, but the staggered relationship between the joints will be maintained throughout as long as the stretch of pavement is straight. At curves, the standard sized mats, at the inside of the curve, may be overlapped a distance greater than those at the outside of the pavement, or off-standard. sized mats may be utilized as seems to be more economic, care being exercised that the endwise joints in a given row are maintained in substantially staggered relationship to such joints in at least the adjacent endwise rows, and preferably in all rows.

Preferably, the laying of the mats is done concurrently from opposite sides of the pavement toward the center, mat length by mat length down the road. Immediately, as a crosswise course of mats is laid, a bed of concrete, for instance, three and one-half inches deep, may be poured directly thereon without necessitating that the respective mats be wired, or otherwise mechanically interlocked, together before the concrete is poured.

, The staggering of the end joints in neighboring rows, as above described, creates a condition in the finished slab such that at no given widthwise cross-section of the roadway, or within a half mat-width thereof, is there more than a percentage equal to one divided by the number of mats across the pavement, or the slab section, where the lengthwise reinforcement is not continuous; and at the fraction of the section where the lengthwise reinforcement is discontinuous in the slab section, the longitudinal reinforcement is lapped a distance suificient to provide a continuity of tension across the splice by the anchorage of the deformations along the bar without regard to transverse wires, or weldments. The discontinuity is also bridged by a mat of at least one, and usually two, adjacent rows. Consequently, if lengthwise stresses in the monolithic structure tend to exceed the strength of the concrete em bedded about the neighboring ends of endwise adjacent mats, such stresses will be absorbed by the sidewise neighboring mat before fracture occurs; and if, in spite of this provision, fractures do occur, they present themselves as hairline cracks at a plurality of points rather than single cracks of such magnitude as to impair the life of the pavement.

Other objects and advantages of the invention will be readily perceived by those skilled in the art when the following description of a specific embodiment is read in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view on a greatly enlarged scale illustrating the shape of the longitudinal Wire used in the reinforcement mat;

FIG. 2 is a schematic view in side elevation showing the wire of FIG. 1 embedded in concrete and a typical diagram of the stresses imposed between wire and concrete;

FIG. 3 is a perspective view of the cross wire used in the reinforcement;

FIG. 4 is a sectional view longitudinally of the pavement showing the lapping in the lengthwise direction of the reinforcement of conventional reinforcement consisting of tied, or welded, mats of wire, or wire mesh;

FIG. 5 is a sectional view longitudinally of the pavement showing the lapping in the reinforcement using the mats constructed in accordance with this invention;

FIG. 6 is an enlarged sectional view taken between the lines E-E and FF of FIG. 5;

FIG. 7 is a schematic plan view of a mat constructed in accordance with this invention and a projection from the end of this mat to illustrate the amount of overlap with the next;

FIG. 8 is a transverse sectional view across the pavement of a reinforcement for a paving showing by projection the amount of overlap edgewise between mats;

FIG. 9 is a schematic plan view illustrating the manner of laying the mats to form a continuous strip of pavement; and

FIG. 10 is a schematic plan view illustrating another manner of laying the mats to form a continuous pavement.

The following description will use the term longitudinal wires to identify the wires running lengthwise in a bar mat and the term cross wire to describe the members running transverse in a mat. Actually, the cross wires are not relied upon to carry other than the actual load across the narrower dimension in a slab. Usually the load on the cross wires, due to crosswire expansion and contraction across the narrower dimension in a slab, is not of great magnitude because of the distance, therefore, these wires can be relatively light and widely spaced thereby redu-cing the weight of the whole mat substantially. Other reasons will appear as this description proceeds. Of course, if the dimensions of a complete slab are great in both directions, cross wires would be used of the same size and spacing as longitudinal wires.

In a slab of reinforced concrete of considerable length, or considerable length and width, the manner in which the loading is transferred between reinforcement (wire mat) and concrete determines the ability of any slab to satisfactorily stand service conditions. With the plain wire mats in general use, the anchorage between any wire lengthwise with respect to the concrete is through the wires welded crosswise to it. For example, in a wire mat reinforced concrete strip of pavement, the anchorages between wires running lengthwise of the strip (longitudinal wires) and the concrete are the cross wires,

and vice versa. Cross wire spacing is usually twelve inches or less on centers. Whereas the total loading on the wires in a plain wire mat is no greater than in any other kind, nevertheless, in such a mat structure, the entire load on any reinforcement wire is through the weldment to the wires running crosswise or normal thereto.-

It will be immediately apparent that the wires of the mat must be large enough so that the weldments will be strong enough to sustain the load. As illustrated by this example which applies to any plain wire mat, it is not just the expected load imposed along a wire which determines its size, but its bearing, or anchorage, in the concrete. As a consequence, the wire sizes in a plain wire mat is a matter determined frequently by arbitrary rules, such as, cross wires can be no smaller than five gauges less than the longitudinal wires regardless of the loading applied lengthwise of a cross wire. Obviously, a penalty in weight is often created by such a rule.

From what has already been said about plain wire mats and their anchorage in a concrete slab, it' can be assumed that the weldments between wires are really the only points of stress transfer between concrete slab and plain wire mat. When a load is applied on any spot to the outer surface of the slab, tension will exist along the opposite side. Since concrete is relatively weak in tension, the slab must depend upon the reinforcement provided by the plain steel wires in the matto resist fracture. Since the resistance to tension available in the mat is only at spaced weldments, then the span of concrete between them is a small part of a much larger span of concrete, which small part has no reinforcement in tension. This small part, having no reinforcement, fails in tension, cracks occur of a width and spacing indicating the failure occurred at one of these small parts because of load distribution over a pavement section usually many feet in length. These cracks get wider and longer as the fracture separates to relieve the stress. Water seeps through the cracks into the underlay. If the slab happens to be in a strip of pavement, then repeated traffic loading causes pumping, pushing away the foundation support adjacent the cracks and further destruction becomes inevitable.

It is now common practice to overlap mats of plain wire at least three feet in a concrete structure in order to have a sufiicient number of wires parallel to this line of the joint between mats to adequately transfer the loads from one mat to the next. Where the wires parallel to the joint are a foot apart, as is customary, this provides three of such wires in one mat adjacent three corresponding wires in the next and, accordingly, three weldments on each wire extending across the joint to anchor a wire extending across the joint from one mat to a wire extending across the joint from the other.

A' typical joint, such as used heretofore between reinforcement mats, is illustrated schematically in FIG. 4. A section of concrete slab 11 about seven inches thick contains the overlapped ends of two mats having longitudinally extending plain wires 13 in one mat and 15 in the other. The distance between anchoring wires 17, 18 and 19 on one mat 13 can be no closer than the thickness of bars 15 to the anchoring wires .20, 21 and 22 in the other mat. The entire stress between mats must be transferred :at only three points along a plane through the slab adjacent wires extending across the joint from each mat. In a fifty foot length of paving, there will be at least three such joints (plain wire mats are fifteen to eighteen feet long), and it is not unforeseeable that one joint would be subject to about all the stress instead of all of the joints stressed alike. If this should occur, tension cracks 24 and 25 at the ends of the shear plane x-y will open up to weaken the joint and thereafter cracks along the shear plane x-y will occur because the concentrated stress imposed at so few anchor points.

The rod used in the wires is a hot rolled deformed shape that is subsequently cold drawn, or cold worked. In the process of manufacture of this rod, a continuous rod is flattened on its opposite sides and the flattened sides formed with spaced segmental shaped ribs. It is then drawn, or cold Worked, through a circular die, or roll set, which clears these ribs, but performs a minimum twenty percent reduction sufiicient to produce the desired work hardening for cold drawn steel having a minimum yield strength of at least sixty thousand pounds per square inch. A piece of Wire 1 so formed is shown in FIG 1 on an enlarged scale. On opposite sides of the wire -1 are flats 7 and 8 ribbed along their surfaces to provide segmental shaped lugs 3, '5 and 9 on the flat 7, and 2, 4

and 6 on the flat 8. These lugs are similar to a segment of a circle of slightly less radius than the final drawn shape of the wire 1.

The spacing between lugs varies with the size of the wire. The bigger the wire, the greater the spacing. Thus, on a large wire, there may be as few as three per inch of length along a side of the section. Smaller wires may have five or more.

FIG. 2 is a view on an enlarged scale illustrating the wire 1 embedded in concrete. The stress diagrams (d) illustrate the distribution of loading between a lag and the concrete in the slab due to a change in relative length between a concrete slab and an embedded reinforcing wire 1. Because of the close spacing of the lugs, thousands of pounds of stress are divided up into small increments acting between a multiplicity of lugs and the surrounding concrete. When so divided, the stress between lug and concrete is far less than the crushing strength of the concrete bearing against the lug. Furthermore, the total force of thousands of pounds may be divided between individual lugs and, when imposed on the section of concrete (b) between any pair of lugs, is much less than the shear strength of a section of concrete having the same dimension (b) along the plane of shear aa. Thus, all that can happen to the concrete from a high differential loading between the slab and wire would be no more than a series of hairline cracks in the slab surface located above, or below, and between the lugs in the slab. These small hairline cracks in the surface of the concrete may open and close slightly as the stress between concrete and reinforcement increases, or decreases. The expansion, or contraction, of these small hairline cracks may be due to temperature change, or loading, but such cracks will be so small as to be almost invisible and, since they are of capillary size, would not permit sufficient seepage to the underlay of a pavement to permit a pumping action on the foundation. This incidentally is a main cause of failure in concrete structure of this kind. Another is caused by frost opening the larger cracks. If the cracks are of capillary size, frost has no significant effect.

In a slab reinforced by a mat having wires constructed as shown in FIG. 1 extending in at least one direction in the concrete slab, the loading imposed on the slab is divided into very small increments by the ribbed surface on the wires. It is characteristic that in such a reinforcement mat any Wire normal to the said one direction carries no more load than a single rib. The strength in any weldment between the ribbed wire and the wire normal thereto is no longer critical to this reinforcing mat.

The manner of anchorage of the ribbed wire in concrete is characterized by a totally different reinforcement. A different stress distribution pattern results from a loading on the top of a slab reinforced by a .mat having the ribbed wire than when reinforced by a mat with plain wire mesh. Because the ribs on the wire are closely spaced anchoring points in the concrete slab, local stresses are imposed on the concrete slab, as shown in FIG. 2, which are in compression and in shear (along plane a-a) under which stresses concrete characteristically excels. Tension in the opposite side of the slab is resisted by these compression and shear forces on each rib along the wire. The rib-s are closely spaced anchoring points in the concrete slab itself. Only the opposite side of the slab adjacent its opposite surface could be subject to any degree of tension and then only for a distance equal to the space between adjacent ribs on the wire. Thus, if failure in tension actually occurs in the slab, it will be evidenced only by closely spaced microscopic cracks through the opposite side of the slab extending inward from the surface. These cracks have no effect upon the strength of the slab, nor will they widen to relieve stress and to permit seepage of water to the underlay. Such cracks do not retain enough water to be likely to result in substantial frost damage. By changing the pattern of stress distribution between concrete and reinforcement to a series of closely space-d points, the nature of the tension cracks due to bending stress on a reinforced slab has been radically changed from wide cracks from surface to surface of a slab and widely spaced, to hairline cracks closely spaced and opening in one surface only. FIGS. and 6 illustrate the manner in which the ribbed wire reinforcement is lapped endwise in the concrete pavement to form a continuous reinforced slab of any desired length. The slab of concrete 31 is approximately seven inches thick, but, in this case, the amount of over- 'lap between mats longitudinally of the slab is only sixteen inches because of the anchorage provided by the ri-be 30 and 34 on opposite sides of the projecting ends 32, and the ribs 36 and 38 on the opposite sides of the projecting ends 33 from the other mat. Looking at the enlarged section of FIG. 6, taken between the lines e-e and f-f, a better idea of force transfer between longitudinal wires extending across the joint can be obtained. Small arrows, indicated as small s, illustrate the stress transfer pattern in the concrete adjacent two of the wires extending across the joint and adjacent one another. As illustrated in FIG. '6, regardless of the direction of the differential in stress between wires and concrete at the lapped joint between mats, stress transfer between wires 32 and 33 distributes itself along the overlapped portion of adjacent wires as a plurality of forces primarily in compression acting between ribs on adjacent sides of the wires 32 and 33. Where the mats are formed in the usual manner with longitudinal wires 32 ribbed, and transverse wires 35 plai-n, arranged in a crisscross pattern, the transverse wires 35 and corresponding wires 37 are subject to no more strain than an individual rib on the wires 32 and 33. Consequently, the weldments between the transverse wires 35, 37 and't-he longitudinal wires 32 and 33 are not depended upon to act as the anchor between mats in a lengthwise direction of the slab.

These three principal differences between the structures of FIG. 4 and FIGS. 5 and 6 eliminate the tendency in the latter to concentrate forces between mats longitud-inally of the slab which will cause the tension cracks 24, 25, illustrated in FIG. 4. In the constructions shown in FIGS. 5 and 6, stress concentrations, due to accumulated stresses at localized points on a plane, are avoided. This permits a laying of the reinforcement mats with sixteen inches overlap instead of three feet. Economy in the weight of steel mat required is obtained by a decrease in the necessary overlap between mats as well as economy in steel in each mat by a decrease in the size wire necessary to provide weldments of suflicient strength. In some instances, the cross wires need be no larger than that necessary to support the mat crosswise for the purpose of handling.

In some instances, it may be advantageous to use ribbed wire extending both longitudinally and transversely of the mat in a crisscross pattern. One example has been set forth above. When ribbed transverse wires are .to be used in a mat instead of plain'wire, then the preferred form for such ribbed wire is illustrated in FIG. 3 as 135. Opposite sides of the wire 135 have flats 107 and 108. On the flat 107 are segment shaped ribs 103, 105, etc., and on the flat 108 are similar ribs 102, 104, etc. This wire 135 is constructed from hot rolled rod in the same manner as the ribbed longitudinal wire 1, except that wire 135 is subject to a different kind of wire straight ening process as a final step in its manufacture. In this final straightening process, the ribbed wire is passed through aligned spaced, stationary, dies. In the space between these dies is a movable die which is driven in an orbital path. The result is shown in FIG. 3, the twist imparted longitudinally of the ribbed wire results from the straightening process. The twist in the wire 135, regardless of how, produced results in one which can roll along a flat surface, and'one which will roll on the like surfaces of another formed by the same or similar straightening process. In one process of manufacture of the mats, the longitudinal ribbed wires are drawn through a welding inachine with multiple welding heads one for each longitudinal wire. The twisted ribbed wires are fed from a hopper located transversely of the longitudinal wires, one at a time onto the longitudinal wires, are pressed against the longitudinal wires, and welded to each simultaneously by the welding heads. Because the twisted ribbed wires will roll on a flat surface and one on another, the hopper feed is successful. Wires that are not straight and round cannot be successfully hopper fed.

A high strength wire mat for a continuous pavement reinforcement is illustrated in FIG. 7. This mat can be constructed of wire of any size to meet specifications. One example for wire sizes suitable for the specific example has been given heretofore. This reinforcement is suitable for continuous pavement (unlimited lengths) twenty-four feet wide and seven inches thick. Each ribbed longitudinal wire 40, in FIG. 7, is twenty-five feet and four inches long. Each ribbed transverse wire 42 is four feet and four inches long.

There are eleven longitudinal wires 40 evenly spaced over a distance of three .feet, six and one-half inches to place them four and one quarter inches center to center. One of these wires 40, atone edge, is spaced one inch on center from the ends of the transverse wires 42. One of these wires 40, at the opposite edge of the mat, is spaced eight and one-half inches on center from the other ends of the transverse wires 42.

There are nineteen transverse wires 42 evenly spaced over a distance of twenty-four feet from the center of a wire 42 at one end of the mat to the center of another wire 42 at the opposite end of the mat. This places the transverse wires 42 a distance of six-teen inches center to center. Both end wires 42 are spaced eight inches oif center from the ends of the longitudinal wires 40.

Where the mats are lapped sixteen inches at the ends, this places two cross wires 42 at the end of adjacent mats one above the other as shown in the embodiment of the invention using plain cross Wires illustrated in FIG. 5.

The exemplary illustration, in FIG. 8, shows one manner of using the mats side by side and the preferred amount of lap, edge to edge, between mats. The transverse section in FIG. 8 shows three mats 61, 62 and 63 in one-half of a slab twenty-four feet wide and a fragment of one of the mats 66 in the other half, it being understood that the portion of the pavement not shown duplicates that shown. Mat 61 is preferably placed on a layer of concrete about three and one-half inches thick poured on the underlay between parallel side rails, such as 80, spaced twenty-four feet apart. Longitudinal wire 40, at the edge of the mat 61, is spaced from the edge of the concrete slab 90 about four inches on center. This means that the end of a transverse wire 42 terminates about three inches in from the edge of the slab 90.

As also shown, the overlap edge to edge between mats is confined to the transverse wires 42 only, and the amount between mats 61, 62 is sufiicient to maintain the uniform spacing of the longitudinal wires 40 between mats at the same distance within a mat, or, four and one quarter inches. This same amount of overlap edge to edge is used between all of the mats except at the pavement center line between mats 63, 66. Here the amount of overlap is about eight inches between transverse wires 42. Again this places a longitudinal wire 40 about four inches on center on each side of the pavement center line. In this instance, each reinforcement mat laid would support a strip of pavement four feet by twenty-four feet, or a net area of ninety-six square feet. This area compares favorably with the eifective area of support provided by plain wire mats, but the mat itself, in this instance, is much lighter, easier handled, and more effective as a reinforcement in the direction of greatest stress. After the mats have been laid on the underlay, a top layer of 9 concrete is poured to form a slab about seven inches thick.

FIGS. 9 and 10 show two different methods of laying mats to form a continuous strip of pavement twenty-four feet wide. In each instance, the concrete is poured between side forms, or rails, 80 and the rails are spaced the width of the pavement, or twenty-four feet.

In FIG. 9, the mats 61 through 72 are laid sequentially in numerical order with the edges overlapped, as shown in FIG. 8, and their ends overlapped as shown in FIG. 5. The mats are intentionally laid so that the ends are staggered, or offset, by about four feet, and end joints between mats are at no place aligned transversely of the pavement. Fill-in mats 91 through 95 finish the end of the pavement off square and are constructed in the same manner as the aforedescr-ibed mats, except the longitudinal wires have lengths of five feet, four inches; nine feet, four inches; thirteen feet, four inches; sevente n feet, four inches; and twenty-one feet, four inches, respectively.

In FIG. 10, the mats 61 through 72' are laid sequentially in numerical order with the edges overlapped, as shown in FIG. 8, and their ends overlapped, as shown in FIG. 5. The mats are again intentionally laid so that the ends are staggered, or offset, by about four feet, and end joints between mats are at no place aligned transversely of the pavement. The fill-in mats 91' through 95' are similar to those shown in FIG. 9 having the same reference character.

In all cases, the mats are either laid on the first strikeoif (a layer of about three inches of concrete in this example) and are progressively extended as the paving rig moves along, or, if desired, the mats can be laid in the same manner before paving by supporting them above the subgrade on metal chairs, or supports, spaced about three feet center to center, or, if desired, placed on top of the poured concrete and pushed down by mechanical means to the proper desired plane, or level, within the slab. In any case, the first three mats on one side and then the three from the other are laid sequentially. There is no need to .tie the mats together.

These alternative methods for laying the reinforcement mats will provide a continuous slab reinforcement without lapping in no less than five-sixths of the pavement width with sutficient reinforcement at the center line of the slab to withstand flexing along this line.

Changes in and modifications of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In the art of constructing substantially continuously longitudinally reinforced concrete slabs, the method comprising:

(a) erecting spaced side forms for confining concrete;

(b) providing a plurality of flat wire mats which are substantially longer than they are wide, whose width is less than the distance between the side forms, and wherein the longitudinal wires are deformed to provide spaced protuberances throughout their length;

(0) laying the mats between the side forms with their longer dimension substantially parallelwith the side forms so that each mat overlaps its sidewise and endwise neighbors, the overlapping ends of endwise neighbors being lapped sidewise by a neighbor of both; and, while the mats are thus overlapped and lapped, pouring and finishing a layer of concrete on and above them.

2. The method of claim 1 wherein the longitudinal wires of the mats are held in spaced relationship by cross wires and the cross wires are spaced substantially farther apart than the longitudinal wires.

3. The method of claim 1 wherein the longitudinal Wires of the mats are held in spaced relationship by cross wires and the cross wires of each mat lap at least one longitudinal wire of the sidewise neighboring mat.

4. The method of claim 1 wherein the overlapping ends of endwise neighbors are at least about a mat-width distant from the nearest end of their sidewise neighbor.

5. The method of claim 4 wherein the overlapping ends of endwise neighbors are substantially disaligned crosswise of the slab with the overlapping ends of other endwise neighbors less than three mat widths distant crosswise therefrom.

6. The method of claim 2 wherein the overlapping ends of endwise neighbors are substantially disaligned crosswise of the slab with the overlapping ends of other endwise neighbors less than three mat-widths distant crosswise therefrom and the disalignment is at least about a mat-width.

References Cited by the Examiner UNITED STATES PATENTS 1,388,544 8/ 1921 Benedict 94-8 1,965,993 7/1934 Sommer et a1. 52-660 2,374,827 5/ 1045 Menzel 52-738 2,655,846 10/ 1953 Freyssinet 94-8 2,787,198 4/1957 White 52-660 3,022,713 2/1962 Fr-iberg 264-34 3,057,270 10/1962 Lee 264-34 3,156,169 11/ 1964 Finsterwalder 94-8 3,214,877 11/ 1965 Akin 52-740 X FOREIGN PATENTS 891,081 3/ 1962 Great Britain.

ALEXANDER H. BRODMERKEL, Primary Examiner.

ROBERT F. WHITE, Examiner.

I. A. FINLAYSON, Assistant Examiner. 

1. IN THE ART OF CONSTRUCTING SUBSTANTIALLY CONTINUOUSLY LONGITUDINALLY REINFORCED CONCRETE SLABS, THE METHOD COMPRISING: (A) ERECTING SPACED SIDE FORMS FOR CONFINING CONCRETE; (B) PROVIDING A PLURLAITY OF FLAT WIRE MATS WHICH ARE SUBSTANTIALLY LONGER THAN THEY ARE WIDE, WHOSE WIDTH IS LESS THAN THE DISTANCE BETWEEN THE SIDE FORMS, AND WHEREIN THE LONGITUDINAL WIRES ARE DEFORMED TO PROVIDE SPACED PROTUBERANCES THROUGHOUT THEIR LENGTH; (C) LAYING THE MATS BETWEEN THE SIDE FORMS WITH THEIR LONGER DIMENSION SUBSTANTIALLY PARALLEL WITH THE SIDE FORMS SO THAT EACH MAT OVERLAPS ITS SIDEWISE AND ENDWISE NEIGHBORS, THE OVERLAPPING ENDS OF ENDWISE NEIGHBORS BEING LAPPED SIDEWISE BY A NEIGHBOR OF BOTH; AND, WHILE THE MATS ARE THUS OVERLAPPED AND LAPPED, POURING AND FINISHING A LAYER OF CONCRETE ON AND ABOVE THEM. 